Our research goals continue to be to learn more about the synthesis of collagen and its control. A major continuing project is the isolation and characterization of collagen mRNAs from chick embryos. The earlier-used Krebs II Ascites system for translating these messages has been replaced by the wheat germ system which shows no endogenous collagen synthesis. Among other isolation approaches, the purification of collagen polysomes by precipitation by antibody against nascent procollagen chains is being developed. Another project is directed at finding out how the cell regulates the relative levels of pro 01 and pro 02 chains. We are attempting to measure the relative number and size of the polysomes in chick embryos cranial bones that make each kind of chain. The role of isoaccepting species of transfer RNA in collagen synthesis is also being probed.